CA2291670C - Method and apparatus for charging boreholes with explosives - Google Patents
Method and apparatus for charging boreholes with explosives Download PDFInfo
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- CA2291670C CA2291670C CA002291670A CA2291670A CA2291670C CA 2291670 C CA2291670 C CA 2291670C CA 002291670 A CA002291670 A CA 002291670A CA 2291670 A CA2291670 A CA 2291670A CA 2291670 C CA2291670 C CA 2291670C
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- explosive
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F42—AMMUNITION; BLASTING
- F42D—BLASTING
- F42D1/00—Blasting methods or apparatus, e.g. loading or tamping
- F42D1/08—Tamping methods; Methods for loading boreholes with explosives; Apparatus therefor
- F42D1/10—Feeding explosives in granular or slurry form; Feeding explosives by pneumatic or hydraulic pressure
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- General Life Sciences & Earth Sciences (AREA)
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- General Engineering & Computer Science (AREA)
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Abstract
A method and a device for charging boreholes (11) with explosives. One end of a charging hose (3) is introduced to a substantially predetermined distan ce from the bottom of the borehole. Subsequently, a pumpable explosive is pumped through the charging hose at a controlled rate and substantially simultaneously with the pumping of the explosive the charging hose is withdrawn from the borehole at a controlled rate. The explosive is caused to flow out from a nozzle (13), arranged on said end of the charging hose (3), in the form of a hollow cone (18) and at high pressure, s o that the outflowing explosive is given increased viscosity and by virtue of the high outflow rate cohesively adheres to the entire cylinder-shaped wall portion (19) of the borehole (11), upon which the explosive impinges in connection with said outflowing. With t he aid of a centring device (14), the nozzle (13) is centred in the borehole (11).< /SDOAB>
Description
METHOD AND APPARATUS FOR CHARGING BOREHOLES WITH
EXPLOSIVES
The present invention relates to a method for chasg-ing boreholes with explosives, comprising the steps of introducing one end of a charging hose into the borehole to a substantially predetermined distance from the bottom of the borehole, pumping a pumpable explosive through the charging hose at a controlled rate and, essentially simultaneously with the pumping of the explosive, with-drawing the charging hose from the borehole at a control-led rate. 10 The invention also relates to an apparatus for charging boreholes with explosives, comprising a vessel -containing a pumpable explosive, a charging;,hose adapted for insertion into a borehole, pumping means connecting -the vessel with the charging hose for transporting the explosive to the borehole and hose operating means for achieving the movement of the charging hose in the bore-hole at a controlled rate:
Specifically, the invention relates to a method and an apparatus for charging pumpable explosives in a reduc-ed amount in relation to the amount corresponding to the complete fill-up of a borehole.
In connection with blasting, it is often suitable to reduce the charge compared to that which corresponds to completely filling up the borehole. One may wish to achieve a smooth and strong final contour, to reduce vibration in connection with blasting or to follow ore faces and reduce undesired waste rock.removal. In driv-ing tunnels or galleries, cautious blasting of the con-tour holes may give a substantially undamaged rock*face with significantly reduced needs for subsequent repair and support work, such as bolting, guniting, concrete reinforcement, etc., and the final profile will be more true to the design size. Similar considerations arise in WO 98/55805 ' = PCT/SE98/00866 underground mining and stoping or in attempts to limit the production of fines to meet certain after-processing requirements. Although numerous closely spaced boreholes can be used to produce smooth fracture planes, the method is limited by practical and economical constraints. ~
One approach could be to use smaller borehole dia-meters in contour or other holes where reduced explo-sive power is desirable. This is impractical and would increase the cost.of blasting as well as render it more difficult. Instead, the trend is towards wider boreholes, which further increases the need for reduced charges.
A second method is to dilute theexplosives.with lightweight materials which reduce the density of the charge. US.4 995 925 describes this method in more detail. However, the product has low water resistance and must be used in.combination with other explosives.
._. . _ "
Common problems associated with the-above-mentioned charging methods are inconsistency in charging_and uncon-trolled coupling between explosive and rock. Detonation failures have also occurred in certain explosives, proba-bly because of precompression from forerunning shock waves in the free gas channel.
A third method, disclosed in US 5 584 222, is to use a string of pumpable or blowable explosive. In the case of a pumpable explosive, the string is obtained by adjusting the withdrawal rate of the charging hose in relation to the product flow rate, i.e. to the speed of the pump. However, the method of using pulverulent or liquid strings is adapted to horizontal or somewhat inclined boreholes.
US 5 105 743 describes a method in which a standard blowable explosive is utilised in partially filling a borehole. The method is limited to particulate and blow-able explosives and is of limited use in, for example, wet environments or.other situations where pumpable explosives are needed.-The method requires different tools for different borehole diameters and tends to result in uneven amounts along the length of the hole.
The present invention is directed towards the provision of a method and an apparatus for charging boreholes with explosives suitable for all borehole directions, but especially for up-holes.
The invention is further directed towards the provision of a method and an apparatus allowing filling of only a desired part of the cross-sectional area of the borehole with a pumpable explosive and allowing the explosive to be distributed as uniformly as possible around the entire borehole wall.
The invention is additionally directed towards the provision, if applicable, draining of the charged borehole of penetrating ground water.
The invention further is directed towards obviating the risk of water pockets forming between the explosive and the borehole wall, when water is used as a lubricant in the charging hose.
In accordance with one aspect of the present invention, there is provided a method according to the introductory paragraph, characterised by causing the explosive to flow out in the form of a hollow cone and at high pressure from a nozzle arranged on said end of the charging hose, so that the outflowing explosive is given increased vicosity and consequently adheres in a cohesive manner to the entire cylinder-shaped wall portion of the borehole, upon which the explosive impinges in connection with said outflowing.
In accordance with a further aspect of the present invention, there is provided an apparatus for carrying out the above-described method characterised in that the apparatus, in addition to the components mentioned by way of introduction, also comprises a nozzle, from which the 3a explosive is caused to flow out in the form of a hollow cone and at high pressure, that the nozzle is fastened to the end of the charging hose by means of a fastening member, and that at least one centring device is arranged on the WO 98/55805 PCT/SE98/00866 =
EXPLOSIVES
The present invention relates to a method for chasg-ing boreholes with explosives, comprising the steps of introducing one end of a charging hose into the borehole to a substantially predetermined distance from the bottom of the borehole, pumping a pumpable explosive through the charging hose at a controlled rate and, essentially simultaneously with the pumping of the explosive, with-drawing the charging hose from the borehole at a control-led rate. 10 The invention also relates to an apparatus for charging boreholes with explosives, comprising a vessel -containing a pumpable explosive, a charging;,hose adapted for insertion into a borehole, pumping means connecting -the vessel with the charging hose for transporting the explosive to the borehole and hose operating means for achieving the movement of the charging hose in the bore-hole at a controlled rate:
Specifically, the invention relates to a method and an apparatus for charging pumpable explosives in a reduc-ed amount in relation to the amount corresponding to the complete fill-up of a borehole.
In connection with blasting, it is often suitable to reduce the charge compared to that which corresponds to completely filling up the borehole. One may wish to achieve a smooth and strong final contour, to reduce vibration in connection with blasting or to follow ore faces and reduce undesired waste rock.removal. In driv-ing tunnels or galleries, cautious blasting of the con-tour holes may give a substantially undamaged rock*face with significantly reduced needs for subsequent repair and support work, such as bolting, guniting, concrete reinforcement, etc., and the final profile will be more true to the design size. Similar considerations arise in WO 98/55805 ' = PCT/SE98/00866 underground mining and stoping or in attempts to limit the production of fines to meet certain after-processing requirements. Although numerous closely spaced boreholes can be used to produce smooth fracture planes, the method is limited by practical and economical constraints. ~
One approach could be to use smaller borehole dia-meters in contour or other holes where reduced explo-sive power is desirable. This is impractical and would increase the cost.of blasting as well as render it more difficult. Instead, the trend is towards wider boreholes, which further increases the need for reduced charges.
A second method is to dilute theexplosives.with lightweight materials which reduce the density of the charge. US.4 995 925 describes this method in more detail. However, the product has low water resistance and must be used in.combination with other explosives.
._. . _ "
Common problems associated with the-above-mentioned charging methods are inconsistency in charging_and uncon-trolled coupling between explosive and rock. Detonation failures have also occurred in certain explosives, proba-bly because of precompression from forerunning shock waves in the free gas channel.
A third method, disclosed in US 5 584 222, is to use a string of pumpable or blowable explosive. In the case of a pumpable explosive, the string is obtained by adjusting the withdrawal rate of the charging hose in relation to the product flow rate, i.e. to the speed of the pump. However, the method of using pulverulent or liquid strings is adapted to horizontal or somewhat inclined boreholes.
US 5 105 743 describes a method in which a standard blowable explosive is utilised in partially filling a borehole. The method is limited to particulate and blow-able explosives and is of limited use in, for example, wet environments or.other situations where pumpable explosives are needed.-The method requires different tools for different borehole diameters and tends to result in uneven amounts along the length of the hole.
The present invention is directed towards the provision of a method and an apparatus for charging boreholes with explosives suitable for all borehole directions, but especially for up-holes.
The invention is further directed towards the provision of a method and an apparatus allowing filling of only a desired part of the cross-sectional area of the borehole with a pumpable explosive and allowing the explosive to be distributed as uniformly as possible around the entire borehole wall.
The invention is additionally directed towards the provision, if applicable, draining of the charged borehole of penetrating ground water.
The invention further is directed towards obviating the risk of water pockets forming between the explosive and the borehole wall, when water is used as a lubricant in the charging hose.
In accordance with one aspect of the present invention, there is provided a method according to the introductory paragraph, characterised by causing the explosive to flow out in the form of a hollow cone and at high pressure from a nozzle arranged on said end of the charging hose, so that the outflowing explosive is given increased vicosity and consequently adheres in a cohesive manner to the entire cylinder-shaped wall portion of the borehole, upon which the explosive impinges in connection with said outflowing.
In accordance with a further aspect of the present invention, there is provided an apparatus for carrying out the above-described method characterised in that the apparatus, in addition to the components mentioned by way of introduction, also comprises a nozzle, from which the 3a explosive is caused to flow out in the form of a hollow cone and at high pressure, that the nozzle is fastened to the end of the charging hose by means of a fastening member, and that at least one centring device is arranged on the WO 98/55805 PCT/SE98/00866 =
charging hose,"which centring device comprises a pair of separate, annular members intended to engage with the outside of the charging hose, as well as a plurality of arcuate, resilient members of considerable length in relation to their width and thickness, which latter mem-bers are orientated essentially in the longitudinal direction of the charging hose and connected to the annu-lar members as well as adapted under compressive stress resiliently to abut against the cylinder-shaped wall of the borehole.
Further developments of the invention will appear from the features recited in the subclaims.
The method according to the invention has no limita-tions withrespect to-the direction of the..borehole, and can thus be applied in vertically upwardly directed holes," in vertically-downwardly'directed holes, in hori-zontal holes,' or in holes of~any:borehole direction.
Nevertheless, the method is particularly advantageous for upwardly directed charging, and particularly if the upwardly directed charging is combined with chemical gassing. By adjusting the degree of charging/amount of explosive to the specific need in each borehole, the range of explosives can be limited to a pumpable emulsion explosive and a primer, and a detonator for initiation.
Moreover, the invention is of great practical importance in all types of charging, where the product is sensitised by means of chemical gassing during and after charging.
The method for achieving partial charging of the borehole consists of pressing emulsion explosive under high pressure through a special nozzle in the hose end.
For the best results, the nozzle is centred in the bore-hole. This is effected by providing the outermost part of the hose with a special centring device, preferably com-prising fastened, resilient lamellae.
The nozzle sprays the explosive in the form of a hollow cone onto the borehole walls, providing very good anchoring to the borehole surface. The desired charging degree according to the invention is-subsequently achiev-ed in the known manner by adjusting the withdrawal of the hose to the flow rate of the explosive, i.e. the pumping and withdrawal rates. The explosive is applied as a 5 cylinder or in the form of a tube to the borehole wall~
while the bottom and the innermost portion of the bore-hole, where the igniting means, i.e. the primer and the detonator, are arranged, are also completely filled with explosive.
By forming a tube of pumpable;explosive, only par-tially filling up a borehole diameter, several objec-tives are achieved. The explosive"itself need not be highly diluted, with corresponding problems; rather ener-gy reduction is accomplished by quantity and by the wall thickness of the explosive tube. Variability in.specific loading is obtained and specifically-it is.possible also to charge some boreholes in their entirety thereby uti-lising the full power of an explosive. Yet the most pro-nounced advantages are obtained in cautious blasting with tubes of small wall thickness of the explosive. It has been found that a tubular pumpable explosive behaves neither as confined nor as unconfined, with high detona-tion velocities. Rather it detonates with markedly reduc-ed velocity and shock generation, perfectly meeting the requirements of cautious blasting. The charging method outlined and the detonation mechanism obtained sustains a stable and undisturbed detonation even in thin tubes, contrary to previous experience. The method is compatible with both microsphere sensitised and gassed explosives.
The latter explosive type may optionally benefit from foaming into the free radical space without axial move-ments. The method requires no auxiliary devices in addi-tion to the explosive itself. The apparatus according to the side claim forms the constructional basis for the critical parts of the charging method, supporting the above-mentioned advantages.
Further developments of the invention will appear from the features recited in the subclaims.
The method according to the invention has no limita-tions withrespect to-the direction of the..borehole, and can thus be applied in vertically upwardly directed holes," in vertically-downwardly'directed holes, in hori-zontal holes,' or in holes of~any:borehole direction.
Nevertheless, the method is particularly advantageous for upwardly directed charging, and particularly if the upwardly directed charging is combined with chemical gassing. By adjusting the degree of charging/amount of explosive to the specific need in each borehole, the range of explosives can be limited to a pumpable emulsion explosive and a primer, and a detonator for initiation.
Moreover, the invention is of great practical importance in all types of charging, where the product is sensitised by means of chemical gassing during and after charging.
The method for achieving partial charging of the borehole consists of pressing emulsion explosive under high pressure through a special nozzle in the hose end.
For the best results, the nozzle is centred in the bore-hole. This is effected by providing the outermost part of the hose with a special centring device, preferably com-prising fastened, resilient lamellae.
The nozzle sprays the explosive in the form of a hollow cone onto the borehole walls, providing very good anchoring to the borehole surface. The desired charging degree according to the invention is-subsequently achiev-ed in the known manner by adjusting the withdrawal of the hose to the flow rate of the explosive, i.e. the pumping and withdrawal rates. The explosive is applied as a 5 cylinder or in the form of a tube to the borehole wall~
while the bottom and the innermost portion of the bore-hole, where the igniting means, i.e. the primer and the detonator, are arranged, are also completely filled with explosive.
By forming a tube of pumpable;explosive, only par-tially filling up a borehole diameter, several objec-tives are achieved. The explosive"itself need not be highly diluted, with corresponding problems; rather ener-gy reduction is accomplished by quantity and by the wall thickness of the explosive tube. Variability in.specific loading is obtained and specifically-it is.possible also to charge some boreholes in their entirety thereby uti-lising the full power of an explosive. Yet the most pro-nounced advantages are obtained in cautious blasting with tubes of small wall thickness of the explosive. It has been found that a tubular pumpable explosive behaves neither as confined nor as unconfined, with high detona-tion velocities. Rather it detonates with markedly reduc-ed velocity and shock generation, perfectly meeting the requirements of cautious blasting. The charging method outlined and the detonation mechanism obtained sustains a stable and undisturbed detonation even in thin tubes, contrary to previous experience. The method is compatible with both microsphere sensitised and gassed explosives.
The latter explosive type may optionally benefit from foaming into the free radical space without axial move-ments. The method requires no auxiliary devices in addi-tion to the explosive itself. The apparatus according to the side claim forms the constructional basis for the critical parts of the charging method, supporting the above-mentioned advantages.
= Although most explosives have a gap sensitivity sufficient to bridge and maintain reaction over certain interruptions in the tube, it is preferred that the formed tube is substantially cohesive over the relevant length without any large thinnings or discontinuities._ Small irregularities are of no significance and may to some extent be unavoidable because of roughness of the borehole walls or other disturbances. The principles of the invention may be used for charging the entire or only part of the borehole length. Generally, it is preferred that the major part of the borehole length is charged with a tube according to the invention.
The tube-may have a systematically varying wall 'thickness over the 'length of the borehole. A preferred kind of variation is.to have a decreasing thickness from 'the inner part of the borehole towards the hole_opening = in order_to meet the requirements for higher;amounts in the innermost partof the hole.:In most applications, though,-it is preferred to have an essentially constant wall thickness.
The method steps are adapted to give an explosive tube with the above-mentioned characteristics. The bore-hole is charged from the bottom or innermost part by pumping the explosive at a controlled rate from a charg-ing hose under simultaneous withdrawal of the hose at a controlled rate. By mutually adjusting the pumping and withdrawal rates, the desired amounts of explosive can be extruded from the hose end. Both rates can vary over time to give either a varying or a constant exiting amount of explosive although it is preferred to keep at least one of the rates constant. When spraying a tube of varying wall thickness, it is preferred to keep the withdrawal rate constant and when spraying a tube of constant'wall thickness.to keep both rates constant.
According to the invention, part of the borehole may be charged differently than with the explosive tube. Spe-cifically, igniting means in the form of detonators and/
The tube-may have a systematically varying wall 'thickness over the 'length of the borehole. A preferred kind of variation is.to have a decreasing thickness from 'the inner part of the borehole towards the hole_opening = in order_to meet the requirements for higher;amounts in the innermost partof the hole.:In most applications, though,-it is preferred to have an essentially constant wall thickness.
The method steps are adapted to give an explosive tube with the above-mentioned characteristics. The bore-hole is charged from the bottom or innermost part by pumping the explosive at a controlled rate from a charg-ing hose under simultaneous withdrawal of the hose at a controlled rate. By mutually adjusting the pumping and withdrawal rates, the desired amounts of explosive can be extruded from the hose end. Both rates can vary over time to give either a varying or a constant exiting amount of explosive although it is preferred to keep at least one of the rates constant. When spraying a tube of varying wall thickness, it is preferred to keep the withdrawal rate constant and when spraying a tube of constant'wall thickness.to keep both rates constant.
According to the invention, part of the borehole may be charged differently than with the explosive tube. Spe-cifically, igniting means in the form of detonators and/
or primers are positioned in the borehole, usually in the innermost part. In order to secure a safe ignition, it is suitable to use an excess of explosive around the ignit-ing means and preferably entirely fill up the borehole diameter around it. Similarly, the outermost borehole,.
parts may need less or no amounts of explosive. Excess charging can be obtained by a delay in hose withdrawal in relation to pump start and a reduction by slowing or stopping pumping. -:
-Partial charging is highly independent of absolute borehole diameter and the charging of explosives accord-ing to the invention maybe utilised for broad-size -ranges. Partial chargingis expressed herein as the cross-sectional area of the-exiting tube in_relation to the cross-sectional area:of the:borehole. In broad terms, the charging degree:thus:expressed may lie between 20 and 100 percent and preferably between 40 and 90 percent.
The exact degree of partial chargingõdepends on the purpose of the reduction. Too high degrees may give insufficient reduction and too low degrees insufficient breakage.
As indicated, in partial charging according to the invention, it is possible, and in cautious blasting desirable, to strive for velocity of detonation (VOD) significantly lower than the velocity obtained both fully confined and fully unconfined. When utilising this possi-bility, the VOD may be between 25 and 100 percent, and preferably between 30 and 80 percent of VOD for the same explosive, in the same tube size, detonated freely on the ground. It may be that the wall thickness of the tube is too thin to detonate freely and in that case the above-mentioned values should be compared with the smallest tube freely detonatable. In absolute terms, VOD may be between 1000 and 6000 m/sec.
Another application for the partial charging accord-ing to the invention is to adapt the charge strength to the specific need in each borehole, i.e. even stoping holes and production holes,:not just contour holes. For this purpose a broader range of partial charging degrees can be used and in particular the higher charging degrees, such as 50 to 95 percent, and preferably 80 to 95 percent. r - According to the invention, at least one borehole is partially charged with an explosive tube for any of the above purposes. In order to take advantage of the flexi-bility of the invention, it is preferred that several boreholes are charged with different charge ratios, in particular several boreholes which are to be blasted in the same round. It..is within the scope of the invention =that any one-of such additional boreholes is fully charg-ed,-i.e. to substantially 100.percent-as above,,in order to"utilise the:full.scope,of the invention.
_'"An"apparatus.for carrying out.the method according to theinvention and for"charging of explosives in a controlled volume.amount per borehole;length unit com-prises a vessel for the explosive and a charging hose for insertion into the borehole as well as a conduit connect-ing these devices. A nozzle is attached to the free end of the charging hose and is centred in the borehole with the aid of one or two successively arranged centring devices on the charging hose, closely adjacent to its free end.
The conduit comprises a pump capable of feeding the pumpable explosive at a controlled and stable volume rate, which rate should preferably be variable in order to allow different degrees of partial charging. Positive displacement pumps giving small flow rate variations, such as eccentric screw pumps, may be used.
If the explosive is to be chemically gassed, the conduit may include an inlet for the gassing agent,' nor-mally a liquid, a vessel for such an-agent, and a pump for transporting and dosing the agent.in the conduit.
In order to reduce the pressure requirement in pumping the explosive, it is suitable to arrange for .the introduction of a lubricating fluid between the hose interior surface and the explosive. The fluid may be water but is preferably an aqueous solution of oxidising salt similar to those present in the explosive itself.
The arrangement may comprise an inlet for the lubricating fluid ending in an annular chamber surrounding the chan-nel of the conduit and having an annular opening towards the channel for forming a liquid ring around the central-ly fed explosive.
The apparatus includes means for moving the hose.
These means should at least permit forward movement of the hose when being inserted into the borehole and driv-ing means for withdrawing the hose ata:controlled rate.
The rate may vary during-the charging operation,-but is preferably constant. Suitably, the driving means also assist in the forward motion of the hose.
Any type of moving means meeting these,requirements can be used for the purposes of the invention.-One type of such moving means comprises opposed wheels or belts, gripping a part of the hose therebetween and driving means connected to at least one of the opposed wheels or belts capable of moving the hose at least in the with-drawal direction. A preferred device of this kind is described in the Swedish patent 8903101-7 (465 566). The device is highly flexible and allows strongly variable feeding speeds both in the forward and in the reverse direction.
Another preferred type of hose moving means com-prises a winder or reel with guiding means for receiving turns of the charging hose on its peripheral part, pre-ferably in a monolayer, and driving means for rotating the winder in a direction withdrawing the hose from the borehole towards the winder at a controlled rate. This device may include disengaging means allowing manual unwinding of the hose during the rotation of the winder.
The guiding means may comprise restricting means for pre-venting radial expansion of hose turns on the winder, except at a-point of.unwinding, whereby the hose is held securely in place on the winder and pushing action is also made possible.
The apparatus should also comprise adjusting means 5 for setting the ratio between the controlled pumping rate and the controlled hose withdrawal rate in order to expel the explosive in the volume rate desired to give said explosive tube characteristics..The adjusting means may include means for varying the pumping rate and/or the 10 withdrawal rate. A simple, yet for many purposes suffi-cient, arrangement is to use adjusting means giving a constant withdrawal rate and a variable pumping rate.
-Hydraulic motors are preferred driving means.for pump and withdrawal means, permitting a wide range of.stable rates : .
In addition to allowing partial filling of_bore-,..
holes, the=invention has:.a number of other,aspects which are of great significance to.the-invention and to its practical use.
By pressing the explosive under high pressure through a narrow nozzle opening, strong turbulence and processing of the emulsion are achieved. This results in increased viscosity of the emulsion, which is desirable, if not to say necessary for upwardly directed holes, and enables the emulsion to remain against the borehole wall by friction as well as enabling cohesion within the high viscosity emulsion. The fact that increased viscosity can be achieved by pressing an emulsion of the type in ques-tion through a narrow slot is known per se, but to effect this by means of a nozzle in the end of the charging hose in upwardly directed charging is a novelty.
In some boreholes, water and water pressure are a problem. In some upwardly directed holes or horizontal holes, water pressure can press the emulsion out of the boreholes if the holes are fully charged. With a partial-ly filled borehole, as described herein, a channel is W O 98/55805, PGT/SE98/00866 created in the explosive allowing draining of the bore-hole.
Another aspect concerns the water used for lubri-cating the inside of the hose according to US Patent 5,584,222. According to this patent, an annular nozzle is used for adding a few percent water (calculated in terms of the emulsion flow) at the start of the charging hose. In this way', a film forms on the inside of the hose, allowing the emulsion to flow more or less like a rod through the hose. This makes it possible to reduce the charging pressure significantly. The technique of using an "aqueous ring" in this manner, is now common practice in emulsion charging, at least s f the hose length exceeds 10-20 m and the charginghose diameter is about-1.5" or less. However, in upwardly directed charg-ing the water creates problems since it may.also lubri-cate the borehole wall and result in the.explosive not remaining where it has been applied-but sliding down-wards. Water pockets may also form. In this context, another important effect of the turbulence and.mixing taking place in the nozzle can be seen: the fact that the water or the aqueous solution is mixed into the emulsion and becomes an integral part of the same.
Another function of the nozzle is to act as a mixer for desensitised emulsion and gassing solution when the emulsion is sensitised by means of chemical gassing. In this way, the transition from a matrix to an explosive takes place in the borehole itself, which is extremely advantageous from a safety point of view. The gassing is effected by means of a chemical reaction between the ammonium ions in the emulsion and the nitrite ions in a gassing solution which is added in a separate conduit, or alternatively as the whole or as a part of the aboVe-men-tioned aqueous ring:
NH2+ + N02 N2 + 2 H20 ~.WO 98/55805 PCT/SE98100866 The evolved nitrogen is present as fine blowholes in the emulsion and constitutes centres of reaction when the explosive is initiated and a shock wave propagates through the explosive.
The evolution of nitrogen results in a volume expAn-sion--of the explosive which, depending on the dosage, usually amounts to 15 to 50% of the original volume of emulsion and gassing agent. In connection with this increase of volume we can observe another important effect of not completely filling the borehole but rather leaving room for the increase in volume. In this way, the expansion can take place radially. This is easier to car-ry out and results in smaller.losses of gas and lower pressure than in the case-of axial expansion,_which occurs in conventional charging when the entire hole-is _..,:filled.
In all of the above-mentioned aspects of:the inven-tion, the nozzle is of major~importance. The,centring equipment has been developed in order to enable the nozzle to distribute the emulsion uniformly around the entire cross-sectional area.
In addition to the mixing function, the cone angle is of major importance. The cone angle shall achieve a balanced distribution of a radial velocity component, providing the required adherence to the borehole wall, and an axial velocity component, ensuring that the emul-sion ends up at a sufficient distance from the front of the hose. In this way, contact between the outside of the hose and the charged emulsion is minimised.
Moreover, it is within the scope of the invention to adjust the charging degree or the size of the tube (the wall thickness of the formed explosive tube) in the same borehole to the most suitable level. In practice this means that, for example, the primer and detonator are positioned at the bottom of the borehole. In order for the primer to become attached it is suitably provided with a locking device in the form of a retaining spring.
parts may need less or no amounts of explosive. Excess charging can be obtained by a delay in hose withdrawal in relation to pump start and a reduction by slowing or stopping pumping. -:
-Partial charging is highly independent of absolute borehole diameter and the charging of explosives accord-ing to the invention maybe utilised for broad-size -ranges. Partial chargingis expressed herein as the cross-sectional area of the-exiting tube in_relation to the cross-sectional area:of the:borehole. In broad terms, the charging degree:thus:expressed may lie between 20 and 100 percent and preferably between 40 and 90 percent.
The exact degree of partial chargingõdepends on the purpose of the reduction. Too high degrees may give insufficient reduction and too low degrees insufficient breakage.
As indicated, in partial charging according to the invention, it is possible, and in cautious blasting desirable, to strive for velocity of detonation (VOD) significantly lower than the velocity obtained both fully confined and fully unconfined. When utilising this possi-bility, the VOD may be between 25 and 100 percent, and preferably between 30 and 80 percent of VOD for the same explosive, in the same tube size, detonated freely on the ground. It may be that the wall thickness of the tube is too thin to detonate freely and in that case the above-mentioned values should be compared with the smallest tube freely detonatable. In absolute terms, VOD may be between 1000 and 6000 m/sec.
Another application for the partial charging accord-ing to the invention is to adapt the charge strength to the specific need in each borehole, i.e. even stoping holes and production holes,:not just contour holes. For this purpose a broader range of partial charging degrees can be used and in particular the higher charging degrees, such as 50 to 95 percent, and preferably 80 to 95 percent. r - According to the invention, at least one borehole is partially charged with an explosive tube for any of the above purposes. In order to take advantage of the flexi-bility of the invention, it is preferred that several boreholes are charged with different charge ratios, in particular several boreholes which are to be blasted in the same round. It..is within the scope of the invention =that any one-of such additional boreholes is fully charg-ed,-i.e. to substantially 100.percent-as above,,in order to"utilise the:full.scope,of the invention.
_'"An"apparatus.for carrying out.the method according to theinvention and for"charging of explosives in a controlled volume.amount per borehole;length unit com-prises a vessel for the explosive and a charging hose for insertion into the borehole as well as a conduit connect-ing these devices. A nozzle is attached to the free end of the charging hose and is centred in the borehole with the aid of one or two successively arranged centring devices on the charging hose, closely adjacent to its free end.
The conduit comprises a pump capable of feeding the pumpable explosive at a controlled and stable volume rate, which rate should preferably be variable in order to allow different degrees of partial charging. Positive displacement pumps giving small flow rate variations, such as eccentric screw pumps, may be used.
If the explosive is to be chemically gassed, the conduit may include an inlet for the gassing agent,' nor-mally a liquid, a vessel for such an-agent, and a pump for transporting and dosing the agent.in the conduit.
In order to reduce the pressure requirement in pumping the explosive, it is suitable to arrange for .the introduction of a lubricating fluid between the hose interior surface and the explosive. The fluid may be water but is preferably an aqueous solution of oxidising salt similar to those present in the explosive itself.
The arrangement may comprise an inlet for the lubricating fluid ending in an annular chamber surrounding the chan-nel of the conduit and having an annular opening towards the channel for forming a liquid ring around the central-ly fed explosive.
The apparatus includes means for moving the hose.
These means should at least permit forward movement of the hose when being inserted into the borehole and driv-ing means for withdrawing the hose ata:controlled rate.
The rate may vary during-the charging operation,-but is preferably constant. Suitably, the driving means also assist in the forward motion of the hose.
Any type of moving means meeting these,requirements can be used for the purposes of the invention.-One type of such moving means comprises opposed wheels or belts, gripping a part of the hose therebetween and driving means connected to at least one of the opposed wheels or belts capable of moving the hose at least in the with-drawal direction. A preferred device of this kind is described in the Swedish patent 8903101-7 (465 566). The device is highly flexible and allows strongly variable feeding speeds both in the forward and in the reverse direction.
Another preferred type of hose moving means com-prises a winder or reel with guiding means for receiving turns of the charging hose on its peripheral part, pre-ferably in a monolayer, and driving means for rotating the winder in a direction withdrawing the hose from the borehole towards the winder at a controlled rate. This device may include disengaging means allowing manual unwinding of the hose during the rotation of the winder.
The guiding means may comprise restricting means for pre-venting radial expansion of hose turns on the winder, except at a-point of.unwinding, whereby the hose is held securely in place on the winder and pushing action is also made possible.
The apparatus should also comprise adjusting means 5 for setting the ratio between the controlled pumping rate and the controlled hose withdrawal rate in order to expel the explosive in the volume rate desired to give said explosive tube characteristics..The adjusting means may include means for varying the pumping rate and/or the 10 withdrawal rate. A simple, yet for many purposes suffi-cient, arrangement is to use adjusting means giving a constant withdrawal rate and a variable pumping rate.
-Hydraulic motors are preferred driving means.for pump and withdrawal means, permitting a wide range of.stable rates : .
In addition to allowing partial filling of_bore-,..
holes, the=invention has:.a number of other,aspects which are of great significance to.the-invention and to its practical use.
By pressing the explosive under high pressure through a narrow nozzle opening, strong turbulence and processing of the emulsion are achieved. This results in increased viscosity of the emulsion, which is desirable, if not to say necessary for upwardly directed holes, and enables the emulsion to remain against the borehole wall by friction as well as enabling cohesion within the high viscosity emulsion. The fact that increased viscosity can be achieved by pressing an emulsion of the type in ques-tion through a narrow slot is known per se, but to effect this by means of a nozzle in the end of the charging hose in upwardly directed charging is a novelty.
In some boreholes, water and water pressure are a problem. In some upwardly directed holes or horizontal holes, water pressure can press the emulsion out of the boreholes if the holes are fully charged. With a partial-ly filled borehole, as described herein, a channel is W O 98/55805, PGT/SE98/00866 created in the explosive allowing draining of the bore-hole.
Another aspect concerns the water used for lubri-cating the inside of the hose according to US Patent 5,584,222. According to this patent, an annular nozzle is used for adding a few percent water (calculated in terms of the emulsion flow) at the start of the charging hose. In this way', a film forms on the inside of the hose, allowing the emulsion to flow more or less like a rod through the hose. This makes it possible to reduce the charging pressure significantly. The technique of using an "aqueous ring" in this manner, is now common practice in emulsion charging, at least s f the hose length exceeds 10-20 m and the charginghose diameter is about-1.5" or less. However, in upwardly directed charg-ing the water creates problems since it may.also lubri-cate the borehole wall and result in the.explosive not remaining where it has been applied-but sliding down-wards. Water pockets may also form. In this context, another important effect of the turbulence and.mixing taking place in the nozzle can be seen: the fact that the water or the aqueous solution is mixed into the emulsion and becomes an integral part of the same.
Another function of the nozzle is to act as a mixer for desensitised emulsion and gassing solution when the emulsion is sensitised by means of chemical gassing. In this way, the transition from a matrix to an explosive takes place in the borehole itself, which is extremely advantageous from a safety point of view. The gassing is effected by means of a chemical reaction between the ammonium ions in the emulsion and the nitrite ions in a gassing solution which is added in a separate conduit, or alternatively as the whole or as a part of the aboVe-men-tioned aqueous ring:
NH2+ + N02 N2 + 2 H20 ~.WO 98/55805 PCT/SE98100866 The evolved nitrogen is present as fine blowholes in the emulsion and constitutes centres of reaction when the explosive is initiated and a shock wave propagates through the explosive.
The evolution of nitrogen results in a volume expAn-sion--of the explosive which, depending on the dosage, usually amounts to 15 to 50% of the original volume of emulsion and gassing agent. In connection with this increase of volume we can observe another important effect of not completely filling the borehole but rather leaving room for the increase in volume. In this way, the expansion can take place radially. This is easier to car-ry out and results in smaller.losses of gas and lower pressure than in the case-of axial expansion,_which occurs in conventional charging when the entire hole-is _..,:filled.
In all of the above-mentioned aspects of:the inven-tion, the nozzle is of major~importance. The,centring equipment has been developed in order to enable the nozzle to distribute the emulsion uniformly around the entire cross-sectional area.
In addition to the mixing function, the cone angle is of major importance. The cone angle shall achieve a balanced distribution of a radial velocity component, providing the required adherence to the borehole wall, and an axial velocity component, ensuring that the emul-sion ends up at a sufficient distance from the front of the hose. In this way, contact between the outside of the hose and the charged emulsion is minimised.
Moreover, it is within the scope of the invention to adjust the charging degree or the size of the tube (the wall thickness of the formed explosive tube) in the same borehole to the most suitable level. In practice this means that, for example, the primer and detonator are positioned at the bottom of the borehole. In order for the primer to become attached it is suitably provided with a locking device in the form of a retaining spring.
Subsequently,~ the charging is effected by withdrawing the charging hose a suitable distance, e.g. 20-80 cm depend-ing on the hole diameter and the pump capacity. In this position, the charging with emulsion explosive begins, initially without withdrawing the hose. When the volurqe around and a few centimetres behind the primer has been filled, but still at a safe distance from the nozzle, the withdrawal of the hose,is initiated. This effect is achieved by means of a timed delay.
The rest of the borehole is then charged by with-drawing the hose while simultaneously spraying emulsion.
As 'stated above, the linear:rate at_which the hose is withdrawn in relation to the flow rate.of the emulsion determines the thickness of_the,ring.orthe.tube in the cross-sectional area..of.the hole. By changing .the flow rate :or the rate _at which _the hoseõ is- withdrawn the size of the'ringcan.be adapted as ,required, e.g. the amount of explosive.per length unit can be reduced in the outer part of the borehole. However, as a.rule,_subsequent to charging the bottom, the same charging degree is utilised in the rest of the hole.
Naturally, it is within the scope of the invention to utilise the present method and apparatus in a single hole in a round or - which is the most practical- in every hole in a round. In each round, the charging degree can then vary according the requirements of different boreholes, for example the charging degree is reduced in the boreholes closest to the contour. Many of the holes are production holes and are normally fully charged. This puts high demands on flow rate control in relation to withdrawal if one wishes to avoid air pockets or soiling the hose. An easier way of handling these problems is to apply the invention also to the "fully charged holes" by filling them to about 95%.
A preferred embodiment of the apparatus according to the invention will now be described by way.of example with reference to the accompanying drawings, in which:
The rest of the borehole is then charged by with-drawing the hose while simultaneously spraying emulsion.
As 'stated above, the linear:rate at_which the hose is withdrawn in relation to the flow rate.of the emulsion determines the thickness of_the,ring.orthe.tube in the cross-sectional area..of.the hole. By changing .the flow rate :or the rate _at which _the hoseõ is- withdrawn the size of the'ringcan.be adapted as ,required, e.g. the amount of explosive.per length unit can be reduced in the outer part of the borehole. However, as a.rule,_subsequent to charging the bottom, the same charging degree is utilised in the rest of the hole.
Naturally, it is within the scope of the invention to utilise the present method and apparatus in a single hole in a round or - which is the most practical- in every hole in a round. In each round, the charging degree can then vary according the requirements of different boreholes, for example the charging degree is reduced in the boreholes closest to the contour. Many of the holes are production holes and are normally fully charged. This puts high demands on flow rate control in relation to withdrawal if one wishes to avoid air pockets or soiling the hose. An easier way of handling these problems is to apply the invention also to the "fully charged holes" by filling them to about 95%.
A preferred embodiment of the apparatus according to the invention will now be described by way.of example with reference to the accompanying drawings, in which:
- Fig. 1 schematically shows the component parts of the -apparatus according to the invention;
Fig. 2 is a schematic, part-sectional perspective view of the nozzle during charging of a borehole with explosive;
Fig. 3 schematically shows the nozzle, its fasten-ing member,-and the free end of the charging hose, prior to assembly and in-axial section;
Fig. 4 showsthe centring device according to the invention; and Fig. 5 schematically shows an inlet member which in a modified embodiment is intended to be,attached between 1,. .
thecharging'hose and the nozzle.
. -õ. .
WithV refe"rence- first to Fig. 1, ,the appa_ratus for charging boreholes-with an"explosive.according to the invention-comprises a.vessel :1:containing a pumpable explosive or matrix, a pump:2, and a charging,hose 3, which is connected to the vessel 1 by the,intermediary of the pump 2. The operation of the pump is adjustable, whereby the flow rate of the explosive can be controlled.
A vessel 4 for lubricant (e.g. water) is preferably con-nected to the charging hose 3 by the intermediary of a pump 5, a flowmeter 6, and an insertion device 7 for lubricant. If desired, a vessel 8 containing a gassing agent may also be connected to the charging hose 3 by the intermediary of a pump 9 and a flowmeter 10 between the pump 2 and the lubricant vessel 4. The gassing agent may also be introduced at the end of the charging hose 3 just before the nozzle 13. The gassing agent is either sup-plied through a separate gassing agent hose 32 running outside the charging hose 3, as indicated by dashed lines in Fig. 1, or the gassing hose is integrated with the charging hose, as indicated by solid lines in the Figure.
Fig..l also shows the free end of the charging hose 3 introduced into a borehole 11 in the rock 12 and with a nozzle 13 attached to said hose end. A pair of centring devices 14 are arranged on the charging hose adjacent to its free end. With-the aid of a hose operating means 15, the charging hose 3, and thus the nozzle 13, are..moved at an adjustable rate in the borehole 11. By adjusting the capacity of the pump and/or the movement of the hose the 5 outflow of explosive is controlled at every point along the length of the borehole 11.
Reference is now made to Fig. 2, which is a more detailed illustration of the charging of a borehole with explosives. When the primer and the detonator/igniter, 10 generally designated 16, have been attached to the bottom or innermost portion of the borehole 11, preferably with a locking device in the form of a retaining spring, and the igniter cord or-hose 17 has:been connected:to the igniting means 16, the charging is carried out by with-15 drawing-the charging hose 3 a suitable distance-from the bottom of the borehole. In this-position, the charging with emulsion explosive begins, initially without with-drawing the hose. When the volume around and a few cen-timetres behind the primer has been filled, but still has not reached the nozzle, the withdrawal of the hose begins. This effect is achieved by means of a timed delay. The nozzle 13 sprays the explosive in the form of a hollow cone 18 towards the cylinder-shaped wall 19 of the borehole 11, the explosive being deposited as a ring in the borehole. Subsequently, the rest of the borehole is charged by withdrawing the hose during simultaneous spraying of emulsion explosive, a hollow cylinder or a tube 20 forming on the wall 19. As stated above, the rate at which the hose is withdrawn in relation to the flow rate of the emulsion determines the share of the cylin-der's cross-sectional area in the cross-sectional area of the hole. By changing the flow rate or the rate at which the hose is withdrawn, the size of the cross-sectiohal area of the cylinder can be adapted as required, e.g. the amount of explosive per length unit can be reduced in the outer part of the borehole. However, as a rule, subse-quent to charging the bottom, the same charging degree is utilised in the rest of the hole. In the thus partially filled borehole a channel 21 is created in the explosive, allowing draining of the borehole 11 or permitting radial expansion in connection with chemical gassing.
Fig. 3 is a sectional exploded view which schemati-cally illustrates the nozzle and a way of attaching it to the free end of the charging hose. The nozzle 13 consists of a substantially cylindrical body 22 with an angled, cone-shaped outlet 23, a swirl chamber 25 with turbulence or mixing members 24 in the central part of the nozzle, a rod 26 connecting the body 22 of the nozzle to an adjust-able head 27, as well as a threaded portion_28 at the otherend of the nozzle for-.connecting to the free end = of -'the -charging hose 3. :_The nozzle "is:utilised both for =efficiently mixing in thelubricating.water/water ring used as'a,lubricant_in the charging.hose,:and for:achiev-ing the spray pattern:in_the form"of a hollowcone. This is achieved by means.of a tangential inflow in the swirl chamber. Different angled outlets and different swirl chamber members give different dispersion angles (about - 120 ) for different charging applications. The nozzle can also be used with no head 27 or rod 26. Other nozzle designs can also_be used.
In the embodiment shown in Fig. 3, the threaded por-25 tion 28 of the nozzle consists of an internal thread for engagement with a fastening member 29 in the form of an exteriorly threaded fastening tube, which in an optional, known manner is fixed to the lumen of the charging hose.
The threaded portion 28 may also consist of an exte-30 rior thread, as shown in the embodiment according to Fig. 2. In that case, the fasting member 29 is suitably an internally threaded sleeve attached to the lumen of the charging hose by means of an integrated or separate nipple member (not shown) in a manner known per se.
An inlet member 30 for a gassing agent can be arranged between the threaded portion 28 and the fasten-ing member 29, cf. Fig. 1, with or without mixing members 31 and with or without a gassing agent admission opening 32 depending upon where in the system the gassing agent is added.
The charging apparatus.according to the invention also comprises at least one, and preferably two, centz-ing device 14 in the area of the free end of the charg-ing hose 3. The centring device_14 is concentrically arranged around the charging hose and comprises a pair of separate, annular members 33, which are in engagement with the outside of the charging hose. A plurality of arcuate, resilient and elongate members 34,-orientated substantially in the longitudinal direction of the charg-ing hose 3,'are equidistantly arranged around.the charg-ing hose and-are attached,-to the annular members.33. Fur-thermore, the length-of the elongate members 34 is consi-derable in relation.to the width_of the annular members 33,' as -can be seen in Fig. 4: ,The -elon.gate members 34 are preferably.lamella-shaped:and form the body of an imagi-nary solid of rotation in the..form of a sphere, an ellip-soid or the like, whose-largest,diameter transversely of the longitudinal direction of the charging hose exceeds the diameter of the borehole 11. In this way, the lamel-lae are caused to abut under compressive stress against the cylinder-shaped wall 19 of the borehole, when the charging hose is introduced into the borehole, and there-by centre the charging hose 3 and thus the nozzle 13 in the borehole, so that the thickness of the tubular wall 20 of the explosive is constant in the circumferential direction at each level in the borehole 11, if the bore-hole is substantially vertical.
The invention is not limited to what has been described above and shown in the drawings, but can be modified within the scope of the appended claims.
Fig. 2 is a schematic, part-sectional perspective view of the nozzle during charging of a borehole with explosive;
Fig. 3 schematically shows the nozzle, its fasten-ing member,-and the free end of the charging hose, prior to assembly and in-axial section;
Fig. 4 showsthe centring device according to the invention; and Fig. 5 schematically shows an inlet member which in a modified embodiment is intended to be,attached between 1,. .
thecharging'hose and the nozzle.
. -õ. .
WithV refe"rence- first to Fig. 1, ,the appa_ratus for charging boreholes-with an"explosive.according to the invention-comprises a.vessel :1:containing a pumpable explosive or matrix, a pump:2, and a charging,hose 3, which is connected to the vessel 1 by the,intermediary of the pump 2. The operation of the pump is adjustable, whereby the flow rate of the explosive can be controlled.
A vessel 4 for lubricant (e.g. water) is preferably con-nected to the charging hose 3 by the intermediary of a pump 5, a flowmeter 6, and an insertion device 7 for lubricant. If desired, a vessel 8 containing a gassing agent may also be connected to the charging hose 3 by the intermediary of a pump 9 and a flowmeter 10 between the pump 2 and the lubricant vessel 4. The gassing agent may also be introduced at the end of the charging hose 3 just before the nozzle 13. The gassing agent is either sup-plied through a separate gassing agent hose 32 running outside the charging hose 3, as indicated by dashed lines in Fig. 1, or the gassing hose is integrated with the charging hose, as indicated by solid lines in the Figure.
Fig..l also shows the free end of the charging hose 3 introduced into a borehole 11 in the rock 12 and with a nozzle 13 attached to said hose end. A pair of centring devices 14 are arranged on the charging hose adjacent to its free end. With-the aid of a hose operating means 15, the charging hose 3, and thus the nozzle 13, are..moved at an adjustable rate in the borehole 11. By adjusting the capacity of the pump and/or the movement of the hose the 5 outflow of explosive is controlled at every point along the length of the borehole 11.
Reference is now made to Fig. 2, which is a more detailed illustration of the charging of a borehole with explosives. When the primer and the detonator/igniter, 10 generally designated 16, have been attached to the bottom or innermost portion of the borehole 11, preferably with a locking device in the form of a retaining spring, and the igniter cord or-hose 17 has:been connected:to the igniting means 16, the charging is carried out by with-15 drawing-the charging hose 3 a suitable distance-from the bottom of the borehole. In this-position, the charging with emulsion explosive begins, initially without with-drawing the hose. When the volume around and a few cen-timetres behind the primer has been filled, but still has not reached the nozzle, the withdrawal of the hose begins. This effect is achieved by means of a timed delay. The nozzle 13 sprays the explosive in the form of a hollow cone 18 towards the cylinder-shaped wall 19 of the borehole 11, the explosive being deposited as a ring in the borehole. Subsequently, the rest of the borehole is charged by withdrawing the hose during simultaneous spraying of emulsion explosive, a hollow cylinder or a tube 20 forming on the wall 19. As stated above, the rate at which the hose is withdrawn in relation to the flow rate of the emulsion determines the share of the cylin-der's cross-sectional area in the cross-sectional area of the hole. By changing the flow rate or the rate at which the hose is withdrawn, the size of the cross-sectiohal area of the cylinder can be adapted as required, e.g. the amount of explosive per length unit can be reduced in the outer part of the borehole. However, as a rule, subse-quent to charging the bottom, the same charging degree is utilised in the rest of the hole. In the thus partially filled borehole a channel 21 is created in the explosive, allowing draining of the borehole 11 or permitting radial expansion in connection with chemical gassing.
Fig. 3 is a sectional exploded view which schemati-cally illustrates the nozzle and a way of attaching it to the free end of the charging hose. The nozzle 13 consists of a substantially cylindrical body 22 with an angled, cone-shaped outlet 23, a swirl chamber 25 with turbulence or mixing members 24 in the central part of the nozzle, a rod 26 connecting the body 22 of the nozzle to an adjust-able head 27, as well as a threaded portion_28 at the otherend of the nozzle for-.connecting to the free end = of -'the -charging hose 3. :_The nozzle "is:utilised both for =efficiently mixing in thelubricating.water/water ring used as'a,lubricant_in the charging.hose,:and for:achiev-ing the spray pattern:in_the form"of a hollowcone. This is achieved by means.of a tangential inflow in the swirl chamber. Different angled outlets and different swirl chamber members give different dispersion angles (about - 120 ) for different charging applications. The nozzle can also be used with no head 27 or rod 26. Other nozzle designs can also_be used.
In the embodiment shown in Fig. 3, the threaded por-25 tion 28 of the nozzle consists of an internal thread for engagement with a fastening member 29 in the form of an exteriorly threaded fastening tube, which in an optional, known manner is fixed to the lumen of the charging hose.
The threaded portion 28 may also consist of an exte-30 rior thread, as shown in the embodiment according to Fig. 2. In that case, the fasting member 29 is suitably an internally threaded sleeve attached to the lumen of the charging hose by means of an integrated or separate nipple member (not shown) in a manner known per se.
An inlet member 30 for a gassing agent can be arranged between the threaded portion 28 and the fasten-ing member 29, cf. Fig. 1, with or without mixing members 31 and with or without a gassing agent admission opening 32 depending upon where in the system the gassing agent is added.
The charging apparatus.according to the invention also comprises at least one, and preferably two, centz-ing device 14 in the area of the free end of the charg-ing hose 3. The centring device_14 is concentrically arranged around the charging hose and comprises a pair of separate, annular members 33, which are in engagement with the outside of the charging hose. A plurality of arcuate, resilient and elongate members 34,-orientated substantially in the longitudinal direction of the charg-ing hose 3,'are equidistantly arranged around.the charg-ing hose and-are attached,-to the annular members.33. Fur-thermore, the length-of the elongate members 34 is consi-derable in relation.to the width_of the annular members 33,' as -can be seen in Fig. 4: ,The -elon.gate members 34 are preferably.lamella-shaped:and form the body of an imagi-nary solid of rotation in the..form of a sphere, an ellip-soid or the like, whose-largest,diameter transversely of the longitudinal direction of the charging hose exceeds the diameter of the borehole 11. In this way, the lamel-lae are caused to abut under compressive stress against the cylinder-shaped wall 19 of the borehole, when the charging hose is introduced into the borehole, and there-by centre the charging hose 3 and thus the nozzle 13 in the borehole, so that the thickness of the tubular wall 20 of the explosive is constant in the circumferential direction at each level in the borehole 11, if the bore-hole is substantially vertical.
The invention is not limited to what has been described above and shown in the drawings, but can be modified within the scope of the appended claims.
Claims (8)
1. A method for charging boreholes with explosives, comprising the steps of introducing one end of a charging hose into the borehole to a substantially predetermined distance from the bottom of the borehole, pumping a pumpable explosive through the charging hose at a controlled rate and, essentially simultaneously with the pumping of the explosive, withdrawing the charging hose from the borehole at a controlled rate, thereby causing the explosive to flow out at high pressure in the form of a hollow cone from a nozzle, arranged on said end of the charging hose, such that the outflowing explosive is given increased viscosity and thereby cohesively adheres to the entire cylinder-shaped wall portion of the borehole upon which the explosive impinges in connection with said outflowing, wherein said pumping and withdrawal rates are adjusted such that the explosive is given a tubular shape on the cylinder-shaped wall of the borehole.
2. A method according to claim 1, wherein the nozzle is kept centered in the borehole during charging.
3. A method according to claim 1 or 2, wherein a film of lubricant, specifically water, is established and maintained between the inside of the charging hose and the explosive and the lubricant is mixed with the explosive in the nozzle for achieving a homogeneous, outflowing mixture from the nozzle.
4. A method according to any one of claims 1 to 3, wherein igniting means is arranged at the bottom of the borehole and said pumping and withdrawal rates are adjusted so that the amount of explosive adjacent to the igniting means exceeds the amount of explosive per length unit in the rest of the borehole.
5. A method according to claim 4, wherein said exceeding amount of explosive is obtained by delaying the withdrawal of the charging hose subsequent to commencing the pumping of the explosive.
6. A method according to any one of claims 1 to 5, wherein the pumpable and cohesive explosive contains a gassing agent and/or a gassing agent is added adjacent to the nozzle.
7. A method according to any one of claims 1 to 6, wherein said pumping and withdrawal rates are adjusted so that the explosive is given a tubular shape of variable wall thickness in the longitudinal direction of the borehole.
8. A method according to claim 7, wherein the explosive is given a tubular shape with a wall thickness decreasing towards the opening of the borehole.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9702151-3 | 1997-06-05 | ||
| SE9702151A SE509273C2 (en) | 1997-06-05 | 1997-06-05 | Method and apparatus for loading boreholes with explosives |
| PCT/SE1998/000866 WO1998055805A1 (en) | 1997-06-05 | 1998-05-12 | Method and apparatus for charging boreholes with explosives |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2291670A1 CA2291670A1 (en) | 1998-12-10 |
| CA2291670C true CA2291670C (en) | 2007-08-21 |
Family
ID=20407266
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002291670A Expired - Fee Related CA2291670C (en) | 1997-06-05 | 1998-05-12 | Method and apparatus for charging boreholes with explosives |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US6397754B1 (en) |
| AU (1) | AU8042698A (en) |
| BR (1) | BR9809730A (en) |
| CA (1) | CA2291670C (en) |
| NO (1) | NO317373B1 (en) |
| SE (1) | SE509273C2 (en) |
| WO (1) | WO1998055805A1 (en) |
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| KR100581174B1 (en) * | 2005-12-29 | 2006-05-18 | 조금원 | Blaster and blasting a method of underwater base rock |
| EP2000764A1 (en) * | 2007-06-04 | 2008-12-10 | Montanuniversität Leoben | A device, charging unit and method of filing a borehole with a explosive material |
| NZ592614A (en) * | 2008-11-06 | 2012-06-29 | Dyno Nobel Asia Pacific Pty Ltd | Explosive charging by spraying the explosive in an arc onto the inner wall of a balst hole |
| EP2472056B1 (en) * | 2010-12-30 | 2016-10-12 | Maxamcorp Holding, S.L. | Borehole inspection system and method for loading explosives in blast boreholes |
| RU2627059C2 (en) | 2013-02-07 | 2017-08-03 | Дайно Нобел Инк. | Delivery systems of explosive materials and methods related to it |
| CN106352748B (en) * | 2016-11-07 | 2018-01-26 | 武汉科技大学 | A kind of pneumatic loading shower nozzle for upper centripetal deep hole |
| CN108592722B (en) * | 2018-04-11 | 2024-03-12 | 贵州贵安新联爆破工程有限公司 | Efficient open-air deep hole blasting fills operation device |
| RU2709123C1 (en) * | 2018-12-28 | 2019-12-16 | Акционерная Компания "АЛРОСА" (публичное акционерное общество) (АК "АЛРОСА" (ПАО)) | Device for charging rising wells and method of charging |
| CN114234749A (en) * | 2021-12-06 | 2022-03-25 | 重庆交通大学 | Deep water hole emulsion explosive releasing device and using method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1202478A (en) * | 1967-08-29 | 1970-08-19 | African Explosives & Chem | Method of and apparatus for loading boreholes |
| ZA706695B (en) * | 1969-11-21 | 1972-05-31 | Ici Australia Ltd | Apparatus for loading boreholes |
| SE8800593L (en) | 1988-02-22 | 1989-08-23 | Nitro Nobel Ab | SPRAENGAEMNESKOMPOSITION |
| SE462508B (en) | 1988-03-15 | 1990-07-02 | Bengt Raadman | PROCEDURE AND DEVICE FOR INTRODUCING EXPLOSIVE SUBSTANCES IN DRILL |
| CA1315573C (en) * | 1989-05-12 | 1993-04-06 | Phil O'garr | Method and apparatus for charging waterlogged boreholes with explosives |
| CA2043926C (en) * | 1991-06-05 | 1996-05-14 | Calvin William Carmichael | Adhesive secondary blasting cone |
| GB9213188D0 (en) * | 1992-06-22 | 1992-08-05 | Solinst Canada Ltd | Introduction of particulate material into a borehole |
| DE4227724A1 (en) * | 1992-08-21 | 1994-02-24 | Preussag Anlagenbau | Method of sinking and sealing an explosive well |
| SE505963C2 (en) * | 1993-02-25 | 1997-10-27 | Nitro Nobel Ab | Method for loading boreholes with explosives |
| AUPM901594A0 (en) * | 1994-10-26 | 1994-11-17 | Ici Australia Operations Proprietary Limited | Apparatus and process for loading upholes with explosives |
| SE504200C2 (en) * | 1995-03-23 | 1996-12-02 | Bofors Liab Ab | Method and apparatus for applying reinforcement charges to boreholes |
| US5841055A (en) * | 1995-10-26 | 1998-11-24 | Eti Explosives Technologies International (Canada) Ltd. | Method for controlled refining of explosive compositions |
-
1997
- 1997-06-05 SE SE9702151A patent/SE509273C2/en not_active IP Right Cessation
-
1998
- 1998-05-12 WO PCT/SE1998/000866 patent/WO1998055805A1/en active Application Filing
- 1998-05-12 CA CA002291670A patent/CA2291670C/en not_active Expired - Fee Related
- 1998-05-12 AU AU80426/98A patent/AU8042698A/en not_active Abandoned
- 1998-05-12 US US09/424,016 patent/US6397754B1/en not_active Expired - Lifetime
- 1998-05-12 BR BR9809730-0A patent/BR9809730A/en not_active IP Right Cessation
-
1999
- 1999-12-03 NO NO19995950A patent/NO317373B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| NO995950D0 (en) | 1999-12-03 |
| SE509273C2 (en) | 1999-01-11 |
| NO995950L (en) | 2000-01-19 |
| SE9702151D0 (en) | 1997-06-05 |
| WO1998055805A1 (en) | 1998-12-10 |
| CA2291670A1 (en) | 1998-12-10 |
| NO317373B1 (en) | 2004-10-18 |
| SE9702151L (en) | 1998-12-06 |
| AU8042698A (en) | 1998-12-21 |
| BR9809730A (en) | 2000-11-14 |
| US6397754B1 (en) | 2002-06-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20150512 |